Downgrading below 3.4 can be fatal for newer Wiis. We've had a few occurences of this in the Brick section where people have followed ancient guides meant for when 3.3 first came out. Also some stupid 4.2 downgrade guides tell people to downgrade to 3.2.
I'm not altogether sure if the reason these Wiis cannot be downgraded is more a hardware issue, rather than software so I would tread carefully if I were you.
By all means try one of the pre-packaged 3.2 Sneek files that were posted a couple of days ago here on Wiihacks.
Not really doing much Wii stuff these days.
I actually released a pre-packaged 3.2 SNEEK (in my sig), and it runs fine as expected. However, since it's a complete emulation, shouldn't it run fine on new Wii's as well, or is the emulation prone to fail on the newer Wiis as much as it is on their actual NAND?